By Pavel Polityuk and Vitalii Hnidyi KYIV (Reuters) – Ukraine became a candidate to join the European Union on Thursday, a bold geopolitical step triggered by Russia’s invasion that Kyiv and Brussels hailed as an “historic moment”. Starting on the long path to EU membership will be a huge boost to morale in the embattled country, as Russian assaults on two cities in the eastern Donbas region move toward a “fearsome climax”, according to a Ukrainian government advisor. “Ukraine’s future is in the EU,” tweeted President Volodymyr Zelenskiy after the official announcement. “A historic moment,” Eu…